Desertification, drought, and despairthat's what global warming has in store for much of Africa. Or so we hear.

Emerging evidence is painting a very different scenario, one in which rising temperatures could benefit millions of Africans in the driest parts of the continent.

Scientists are now seeing signals that the Sahara desert and surrounding regions are greening due to increasing rainfall.

If sustained, these rains could revitalize drought-ravaged regions, reclaiming them for farming communities.

This desert-shrinking trend is supported by climate models, which predict a return to conditions that turned the Sahara into a lush savanna some 12,000 years ago.

Green Shoots

The green shoots of recovery are showing up on satellite images of regions including the Sahel, a semi-desert zone bordering the Sahara to the south that stretches some 2,400 miles (3,860 kilometers).

Images taken between 1982 and 2002 revealed extensive regreening throughout the Sahel, according to a new study in the journal Biogeosciences.

The study suggests huge increases in vegetation in areas including central Chad and western Sudan.

The transition may be occurring because hotter air has more capacity to hold moisture, which in turn creates more rain, said Martin Claussen of the Max Planck Institute for Meteorology in Hamburg, Germany, who was not involved in the new study.

"The water-holding capacity of the air is the main driving force," Claussen said.

He added that the greening trend is supported by other satellite data.

'The desert crocodiles have adapted to the changing environment in northern Africa; 8,000 to 10,000 years ago, what is now desert was probably lush savannah and grasslands. Today the Sahara is hot and arid, the land sandy, rainfall minimal, and vegetation sparse.

"The extension of range almost certainly reflects climatic changes," said Ross. "We know that even in Roman times, the Sahara was much wetter and greener than it is now. As these places slowly dried up, remnant populations became isolated from the other crocodiles on the continent. How these populations adapted to the changing conditions is most interesting." '

Of course there are observable climate cycles in that part of the world. All of human history verifies that. The Nile valley, for example, was one of the most lush growing areas in the ancient world.

More recently, the fall of the Western Roman empire was precipitated by (among many other things) the Vandals in their sweep through what is now Spain and their capture of northern Africa, significant because that was Rome's granary. Yes, they grew wheat there ("corn" if you're reading Gibbon), enough to support an imperial city. That was not quite 1600 years ago.

Wheat in North Africa. Wineries in Britain. These things are all a part of the historical record, and any climate model that can't account for them is simply inadequate.

Much of what is now the northern Sahara desert was part of the Numadian Empire in Hannibal's day, a mere 2300 years ago or so. The Numadians were Allies of Carthage and historians describe their land as lush and tropical. They were also the source for Hannibal's famous elephants.

I guess the chariots stirred up a lot of global warming back then.

12
posted on 08/02/2009 7:07:38 PM PDT
by Vigilanteman
(Are there any men left in Washington? Or, are there only cowards? Ahmad Shah Massoud)

“The transition may be occurring because hotter air has more capacity to hold moisture, which in turn creates more rain, said Martin Claussen of the Max Planck Institute for Meteorology in Hamburg, Germany, who was not involved in the new study.”

Let me get this straight. The desert is already hot. But, if it gets hotter it will become greener. OK, got it.

[Let me get this straight. The desert is already hot. But, if it gets hotter it will become greener. OK, got it.

Is this like boiling something until it freezes?]

Deserts are defined by their being dry - not by being hot - there are plenty of cold deserts. If the global atmospheric temperature rises by a small amount, then the moisture carrying capacity of the air will increase by a proportionate amount. More water vapor in the air = more precipitation worldwide. And more precipitation worldwide = shrinking deserts.

17
posted on 08/02/2009 8:05:46 PM PDT
by spinestein
(The answer is 42.)

Disclaimer:
Opinions posted on Free Republic are those of the individual
posters and do not necessarily represent the opinion of Free Republic or its
management. All materials posted herein are protected by copyright law and the
exemption for fair use of copyrighted works.